Subduction zones play a fundamental role in our daily life: half of the world’s population lives on top or nearby one of them, in coastal areas repeatedly devastated by large earthquakes, tsunamis or volcanic eruptions. These dramatic phenomena are fundamentally controlled by processes at and across subduction zone inter-plate boundaries, where stresses and energy release via earthquakes together with fluid-mediated mass transfer interact on a wide range of spatial and temporal scales (from 10-4 to 106-7 yr). Unfortunately,the nature, structure and properties of this plate interface are still largely unknown, calling for a thorough Zoom In between the Plates (ZIP).